'\" et
.TH POSIX_TRACE_CREATE "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
posix_trace_create,
posix_trace_create_withlog,
posix_trace_flush,
posix_trace_shutdown
\(em trace stream initialization, flush, and shutdown from a process
(\fBTRACING\fP)
.SH SYNOPSIS
.LP
.nf
#include <sys/types.h>
#include <trace.h>
.P
int posix_trace_create(pid_t \fIpid\fP,
    const trace_attr_t *restrict \fIattr\fP,
    trace_id_t *restrict \fItrid\fP);
int posix_trace_create_withlog(pid_t \fIpid\fP,
    const trace_attr_t *restrict \fIattr\fP, int \fIfile_desc\fP,
    trace_id_t *restrict \fItrid\fP);
int posix_trace_flush(trace_id_t \fItrid\fP);
int posix_trace_shutdown(trace_id_t \fItrid\fP);
.fi
.SH DESCRIPTION
The
\fIposix_trace_create\fR()
function shall create an active trace stream. It allocates all the
resources needed by the trace stream being created for tracing the
process specified by
.IR pid
in accordance with the
.IR attr
argument. The
.IR attr
argument represents the initial attributes of the trace stream and
shall have been initialized by the function
\fIposix_trace_attr_init\fR()
prior to the
\fIposix_trace_create\fR()
call. If the argument
.IR attr
is NULL, the default attributes shall be used. The
.IR attr
attributes object shall be manipulated through a set of functions
described in the
.IR posix_trace_attr
family of functions. If the attributes of the object pointed to by
.IR attr
are modified later, the attributes of the trace stream shall not be
affected. The
.IR creation-time
attribute of the newly created trace stream shall be set to the value
of the system clock, if the Timers option is not supported, or to the
value of the CLOCK_REALTIME clock, if the Timers option is supported.
.P
The
.IR pid
argument represents the target process to be traced. If the process
executing this function does not have appropriate privileges to trace
the process identified by
.IR pid ,
an error shall be returned. If the
.IR pid
argument is zero, the calling process shall be traced.
.P
The
\fIposix_trace_create\fR()
function shall store the trace stream identifier of the new trace
stream in the object pointed to by the
.IR trid
argument. This trace stream identifier shall be used in subsequent
calls to control tracing. The
.IR trid
argument may only be used by the following functions:
.TS
tab(!);
l l.
T{
.nf
\fIposix_trace_clear\fR()
\fIposix_trace_eventid_equal\fR()
\fIposix_trace_eventid_get_name\fR()
\fIposix_trace_eventtypelist_getnext_id\fR()
\fIposix_trace_eventtypelist_rewind\fR()
\fIposix_trace_get_attr\fR()
\fIposix_trace_get_status\fR()
T}!T{
.nf
\fIposix_trace_getnext_event\fR()
\fIposix_trace_shutdown\fR()
\fIposix_trace_start\fR()
\fIposix_trace_stop\fR()
\fIposix_trace_timedgetnext_event\fR()
\fIposix_trace_trid_eventid_open\fR()
\fIposix_trace_trygetnext_event\fR()
.fi
T}
.TE
.P
If the Trace Event Filter option is supported, the following additional
functions may use the
.IR trid
argument:
.TS
tab(!);
l l.
T{
\fIposix_trace_get_filter\fR()
T}!T{
\fIposix_trace_set_filter\fR()
T}
.TE
.P
In particular, notice that the operations normally used by a trace
analyzer process, such as
\fIposix_trace_rewind\fR()
or
\fIposix_trace_close\fR(),
cannot be invoked using the trace stream identifier returned by the
\fIposix_trace_create\fR()
function.
.P
A trace stream shall be created in a suspended state.
If the Trace Event Filter option is supported, its trace event type
filter shall be empty.
.P
The
\fIposix_trace_create\fR()
function may be called multiple times from the same or different
processes, with the system-wide limit indicated by the runtime
invariant value
{TRACE_SYS_MAX},
which has the minimum value
{_POSIX_TRACE_SYS_MAX}.
.P
The trace stream identifier returned by the
\fIposix_trace_create\fR()
function in the argument pointed to by
.IR trid
is valid only in the process that made the function call. If it is
used from another process, that is a child process, in functions
defined in POSIX.1\(hy2008, these functions shall return with the error
.BR [EINVAL] .
.P
The
\fIposix_trace_create_withlog\fR()
function shall be equivalent to
\fIposix_trace_create\fR(),
except that it associates a trace log with this stream. The
.IR file_desc
argument shall be the file descriptor designating the trace log
destination. The function shall fail if this file descriptor refers to
a file with a file type that is not compatible with the log policy
associated with the trace log. The list of the appropriate file types
that are compatible with each log policy is implementation-defined.
.P
The
\fIposix_trace_create_withlog\fR()
function shall return in the parameter pointed to by
.IR trid
the trace stream identifier, which uniquely identifies the newly
created trace stream, and shall be used in subsequent calls to control
tracing. The
.IR trid
argument may only be used by the following functions:
.TS
tab(!);
l l.
T{
.nf
\fIposix_trace_clear\fR()
\fIposix_trace_eventid_equal\fR()
\fIposix_trace_eventid_get_name\fR()
\fIposix_trace_eventtypelist_getnext_id\fR()
\fIposix_trace_eventtypelist_rewind\fR()
\fIposix_trace_flush\fR()
\fIposix_trace_get_attr\fR()
T}!T{
.nf
\fIposix_trace_get_status\fR()
\fIposix_trace_getnext_event\fR()
\fIposix_trace_shutdown\fR()
\fIposix_trace_start\fR()
\fIposix_trace_stop\fR()
\fIposix_trace_timedgetnext_event\fR()
\fIposix_trace_trid_eventid_open\fR()
.fi
T}
.TE
.P
If the Trace Event Filter option is supported, the following additional
functions may use the
.IR trid
argument:
.TS
tab(!);
l l.
T{
\fIposix_trace_get_filter\fR()
T}!T{
\fIposix_trace_set_filter\fR()
T}
.TE
.P
In particular, notice that the operations normally used by a trace
analyzer process, such as
\fIposix_trace_rewind\fR()
or
\fIposix_trace_close\fR(),
cannot be invoked using the trace stream identifier returned by the
\fIposix_trace_create_withlog\fR()
function.
.P
The
\fIposix_trace_flush\fR()
function shall initiate a flush operation which copies the contents of
the trace stream identified by the argument
.IR trid
into the trace log associated with the trace stream at the creation
time. If no trace log has been associated with the trace stream
pointed to by
.IR trid ,
this function shall return an error. The termination of the flush
operation can be polled by the
\fIposix_trace_get_status\fR()
function. During the flush operation, it shall be possible to trace
new trace events up to the point when the trace stream becomes full.
After flushing is completed, the space used by the flushed trace events
shall be available for tracing new trace events.
.P
If flushing the trace stream causes the resulting trace log to become
full, the trace log full policy shall be applied. If the trace
.IR log-full-policy
attribute is set, the following occurs:
.IP POSIX_TRACE_UNTIL_FULL 6
.br
The trace events that have not yet been flushed shall be discarded.
.IP POSIX_TRACE_LOOP 6
.br
The trace events that have not yet been flushed shall be written to the
beginning of the trace log, overwriting previous trace events stored
there.
.IP POSIX_TRACE_APPEND 6
.br
The trace events that have not yet been flushed shall be appended to the
trace log.
.P
The
\fIposix_trace_shutdown\fR()
function shall stop the tracing of trace events in the trace stream
identified by
.IR trid ,
as if
\fIposix_trace_stop\fR()
had been invoked. The
\fIposix_trace_shutdown\fR()
function shall free all the resources associated with the trace
stream.
.P
The
\fIposix_trace_shutdown\fR()
function shall not return until all the resources associated with the
trace stream have been freed. When the
\fIposix_trace_shutdown\fR()
function returns, the
.IR trid
argument becomes an invalid trace stream identifier. A call to this
function shall unconditionally deallocate the resources regardless of
whether all trace events have been retrieved by the analyzer process.
Any thread blocked on one of the
\fItrace_getnext_event\fR()
functions (which specified this
.IR trid )
before this call is unblocked with the error
.BR [EINVAL] .
.P
If the process exits, invokes a member of the
.IR exec
family of functions, or is terminated, the trace streams that the
process had created and that have not yet been shut down, shall be
automatically shut down as if an explicit call were made to the
\fIposix_trace_shutdown\fR()
function.
.P
For an active trace stream with log, when the
\fIposix_trace_shutdown\fR()
function is called, all trace events that have not yet been flushed to
the trace log shall be flushed, as in the
\fIposix_trace_flush\fR()
function, and the trace log shall be closed.
.P
When a trace log is closed, all the information that may be retrieved
later from the trace log through the trace interface shall have been
written to the trace log. This information includes the trace
attributes, the list of trace event types (with the mapping between
trace event names and trace event type identifiers), and the trace
status.
.P
In addition, unspecified information shall be written to the trace
log to allow detection of a valid trace log during the
\fIposix_trace_open\fR()
operation.
.P
The
\fIposix_trace_shutdown\fR()
function shall not return until all trace events have been flushed.
.SH "RETURN VALUE"
Upon successful completion, these functions shall return a value of
zero. Otherwise, they shall return the corresponding error number.
.P
The
\fIposix_trace_create\fR()
and
\fIposix_trace_create_withlog\fR()
functions store the trace stream identifier value in the object
pointed to by
.IR trid ,
if successful.
.SH ERRORS
The
\fIposix_trace_create\fR()
and
\fIposix_trace_create_withlog\fR()
functions shall fail if:
.TP
.BR EAGAIN
No more trace streams can be started now.
{TRACE_SYS_MAX}
has been exceeded.
.TP
.BR EINTR
The operation was interrupted by a signal. No trace stream was
created.
.TP
.BR EINVAL
One or more of the trace parameters specified by the
.IR attr
parameter is invalid.
.TP
.BR ENOMEM
The implementation does not currently have sufficient memory to create
the trace stream with the specified parameters.
.TP
.BR EPERM
The caller does not have appropriate privileges to trace the process
specified by
.IR pid .
.TP
.BR ESRCH
The
.IR pid
argument does not refer to an existing process.
.P
The
\fIposix_trace_create_withlog\fR()
function shall fail if:
.TP
.BR EBADF
The
.IR file_desc
argument is not a valid file descriptor open for writing.
.TP
.BR EINVAL
The
.IR file_desc
argument refers to a file with a file type that does not support the
log policy associated with the trace log.
.TP
.BR ENOSPC
No space left on device. The device corresponding to the argument
.IR file_desc
does not contain the space required to create this trace log.
.P
The
\fIposix_trace_flush\fR()
and
\fIposix_trace_shutdown\fR()
functions shall fail if:
.TP
.BR EINVAL
The value of the
.IR trid
argument does not correspond to an active trace stream with log.
.TP
.BR EFBIG
The trace log file has attempted to exceed an implementation-defined
maximum file size.
.TP
.BR ENOSPC
No space left on device.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
None.
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
The
\fIposix_trace_create\fR(),
\fIposix_trace_create_withlog\fR(),
\fIposix_trace_flush\fR(),
and
\fIposix_trace_shutdown\fR()
functions may be removed in a future version.
.SH "SEE ALSO"
.ad l
.IR "\fIclock_getres\fR\^(\|)",
.IR "\fIexec\fR\^",
.IR "\fIposix_trace_attr_destroy\fR\^(\|)",
.IR "\fIposix_trace_clear\fR\^(\|)",
.IR "\fIposix_trace_close\fR\^(\|)",
.IR "\fIposix_trace_eventid_equal\fR\^(\|)",
.IR "\fIposix_trace_eventtypelist_getnext_id\fR\^(\|)",
.IR "\fIposix_trace_get_attr\fR\^(\|)",
.IR "\fIposix_trace_get_filter\fR\^(\|)",
.IR "\fIposix_trace_getnext_event\fR\^(\|)",
.IR "\fIposix_trace_start\fR\^(\|)",
.IR "\fIposix_trace_start\fR\^(\|)",
.IR "\fItime\fR\^(\|)"
.ad b
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<sys_types.h>\fP",
.IR "\fB<trace.h>\fP"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
